Slurry concentrating apparatus



Nov. 12, 1968 F|ER$T|NE 3,410,480

SLURRY CONCENTRAT ING APPARATUS Filed May 5, 1967 2 Sheets-Sheet l INVENTOR. u BURTON A. FIERSTINE Nov. 12, 1968 B. A. FIERSTINE SLURRY CONCENTRATING APPARATUS 2 Sheets-Sheet 2 Filed May 5, 1967 FIG. 2.

'llllk FIG. 4.

INVENTOR.

3 BURTON A. FIERSTINE .l'g g a u s United States Patent Office 3,410,480 Patented Nov. 12, 1968 3,410,480 SLURRY CONCENTRATING APPARATUS Burton A. Fierstine, Saginaw, Mich, assignor to Baker Perkins Inc., Saginaw, Mich., a corporation of New York Filed May 5, 1967, Ser. N0. 636,427 11 Claims. (Cl. 233-20) ABSTRACT OF THE DISCLOSURE slurry.

Slurry concentrating apparatus This invention relates to apparatus for concentrating slurries of particulate solid material in a liquid, and more particularly to apparatus which is adapted to increase the solids content percentage of a dilute slurry by the separation of liquid from the slurry.

Basis of the invention The solid components of slurries may be substantially separated from the liquid components by the effect of centrifugal forces in centrifuging machines of various design and construction. In conventional machines the liquid is moved by centrifugal force through apertures in the rotating basket wall of the machine and the solids are retained in the rotating basket and discharged axially. The efficiency of such machines may be considerably increased if the slurries are preconcentrated.

An object of the present invention is to provide novel apparatus which is specifically designed and adapted for the highly efiicient concentration of slurries.

Another object of the present invention is the provision of novel apparatus for the concentration of the solids in slurries with the aid of centrifugal forces.

Still another object of the invention is the provision of a novel process for the enrichment of slurries in a continuous operation comprising distinct cycles of the step of concentrating the solids and concentrated slurry.

Other objects will become apparent from the following detailed description in conjunction with the attached drawings.

Drawings which may be utilized in the automatic operation of the concentrator.

Detailed description of the invention Referring now in the first instance to FIGURES 1 and 2 of the drawings, the slurry concentrator includes a generally frustoconical housing generally designated 20,

the step of discharging the which is journaled at its right end (FIGURE 1) in a bearing 21 and supported at its left end on a tubular shaft 22 which is in turn journaled by a bearing 23 for rotation about an essentially horizontal axis of rotation a. The bearing 21 is mounted in vertical structural member 24 and bearing 23 is mounted in vertical structural member 25, both of which may be structurally connected to a base 26. The housing comprises an essentially conical wall portion 27 with a cylindrical portion 28 at the left. It is closed at its left end by a front plate 29 having a central circular aperture accommodating a hub portion 29a of plate 29. The hub 29a surrounds a reciprocable end member 30 which is slidably mounted on the shaft 22. A liquid seal is effected between hub 29a and end member 30 by suitable packing rings 31, and a seal is effected between shaft 22 and end member 30 by packing 32 so that the member 30 may be axially reciprocated on shaft 22 without breaking the seal between housing 20 and shaft 22. A coaxial tubular liquid outlet bore 34 is provided in shaft 22 and includes portions 35 and 36 of larger diameter, the portion 36 comprising a tube which projects coaxially into the interior of the housing 20 and a helical coil spring 37 extending between end member 30 and the opposite end of housing 20. An outlet pipe 34a connects with the bore 34.

At the right end of housing 20 a diverging coaxial passage 20a accommodates a slurry delivery or feed pipe D for feeding the slurry to be concentrated to the device. Mounted on the pipe D is an inverted, cup-shaped feed directing member 38 provided in the path of the incoming slurry so as to direct its flow along the walls of the feed funnel 20a, as indicated by the arrows. A pulley portion 20b with a belt 39 connected to suitable driving means (not shown) for rapidly rotating the housing 20 is formed on the right end of the housing 20 as shown and seal rings 200 may be provided between the housing 20 and stationary delivery pipe D as shown.

Around the inner circumference of the wall 27 of housing 20 are fixedly mounted ribs 20d which guide the spring when it is being compressed and when it is expanding. Between the individual convolutions of the round crosssection spring 37 are interposed the coils of a sealing helical fiat spring 40 which is of identical outer diameter so that the flat spring is supported and also guided by the radially inner edges of ribs 20a. The spring 40 is made from a fiat, band-like width, helically wound to form an essentially cylindrical coil. The individual convolutions of the fiat spring 40 preferably form weir-like bafiles 41 within the tubular structure defined by the main spring 27 with the width of the individual convolutions 41 progressively increasing from right to left so that the inner edges of the flat spring 40 define an open fiustoconical passage in the interior of the main spring 37. The left end convolution of spring 40 fits closely around the outer circumference of tubular outlet pipe 34a.

the bottom of stationary housing 43 a chute-like slurry outlet 46 is provided for collecting concentrated slurry and forwarding it to'storage or further processing equipment. Mounted on support 25 to compress the springs 37 and 40 is a double-acting fluid pressure powered cylinder 47 having a piston rod 48 with a roller 49 bearing against the face of end member 30.

The tubular structure formed by combined flat and round cross-section springs 37 and 40 is illustrated in FIGURE 1 in open position, leaving passages 50 between the individual convolutions of the springs. For the concentrating operation of the apparatus the passages between the convolutions of the springs are initially closed by activating the power cylinder 47 so that rod 48 pushes end member 30 to the right in FIGURE 1 until the coils are completely compressed and closed in essentially liquidtight relationship at their cylindrical circumferences by close contact between the individual neighboring convolutions of the two springs 37 and 40. The housing and helical springs 37 and 40 are preferably continuously rapidly axially rotated by driving belt 39 and the slurry to be concentrated is introduced through feed pipe D and directed by distributor 38 against the wall of flaring inlet 20a from where it passes, under the effect of the centrifugal forces, into the interior of the rotating cylindrical structure formed by the closed springs 37 and 40. The slurry gradually assumes a rotational motion and is subjected to centrifugal forces so that the heavier solid particles are predominantly deposited against the springs 37 and 40, and the lighter fluid is predominantly collected in the radially inner portions of the rotating slurry annulus. At the same time, the slurry flows gradually to the left, undulating over and around the weir-like bafiles 41 formed by the progressively enlarging convolutions of fiat spring 40, which enhances the separating process. The flow of the slurry in the undulating zig-zag path, while it is subjected to the centrifugal forces, aids further the separation of the solids from the liquid, so that in the left section of the cylindrical spring structure a core of essentially solid free liquid is surrounded by slurry of increasing solids content. The essentially solids-free liquid flows out through tubular outlet 36 and through bore 34 to leave the apparatus through outlet conduit 34a. When sufiicient quantities of solids and of concentrated slurry have been deposited and collected around the inner periphery of the cylindrical structure formed by springs 37 and 40, the power cylinder 47 is reversed. This permits the springs 37 and 40 to expand, opening up the passages 50 between the convolutions of the springs to a predetermined degree. Under the elfect of the centrifugal forces, the solids and concentrated slurry, respectively, are thereby quickly thrown out of the cylindrical structure, moving through passages 50 into the housing 20 and to openings 42, to be collected in stationary housing 43 from whence they flow out through slurry outlet chute 46.

When the concentrated slurry has been removed from the cylindrical passage formed by the springs 37 and 40, the cylinder 47 is activated again so that the springs are compressed into a closed position to commence a new cycle of slurry concentration, deposition, and discharge.

The time required for carrying out the steps of each cycle of operation depends on various factors, such as the feed rate of the slurry to the apparatus, the solids content of the slurry fed to the apparatus, the physical and chemical nature and the relative specific weights of the solid and of the liquid, the desired ratio of concentrations of the slurry fed into the apparatus and the slurry to be recovered from the apparatus, etc. Generally, the time required for the concentration and deposition of the concentrated slurry is considerably longer than the time required for the opening of the passages 50 between the springs and the discharge of the collected slurry. A typical time schedule of one cycle is diagrammatically represented in FIGURE 3 of the attached drawings with the time in seconds represented on the abscissa x-y and the state of closing of the passages represented by the ordinate w-x. The passages are completely closed at wand fully opened at x. In the cycle represented by way of example in FIGURE 3 the time required for the closing of the passages is one second, the time required for the concentration and deposition of the concentrated slurry is four seconds, and the time required for decompression and extension of the spring to its fully open position is again one second, i.e., in a cycle of a total of six seconds, the springs are completely closed for two-thirds of the time or for four seconds, respectively. With the slurry concentrating apparatus of the invention, a given composition of the feed slurry, and a predetermined, desired concentration ratio, the time cycle and the optimum feed rate may be readily determined by simple experiment.

Instead of controlling the cycle by hand it is perferable to provide electrical control means which automatically control the operation of the power cylinder 47. A circuit useful for this purpose is illustrated in FIGURE 4 and comprises an electrical power source at 51, to which are connected two cam actuated electrical switches 52 and 53, each contained in a separate circuit, and each circuit including an advance solenoid 54 and a retract solenoid 55 for the control of the valves regulating the flow of the fluid to and from the opposite ends of cylinder 47. This spring control may also be achieved with suitable mechanical means such as mechanically rotated cam devices or the like at a suitable rate to produce the desired cycle of closing and opening of the passages 50.

Suitable slurries which may be concentrated in the apparatus of the invention may have any desired composition. Examples are dispersions of salt crystals in brine, sugar crystals in molasses solutions, sand dispersed in water, finely particulate coal or ores dispersed in water, and fibers such as cotton linters suspended in 'water.

The apparatus has been described hereirrbefore with the convolutions of a flat spring interposed between the convolutions of a round cross-section main spring. The use of a round cross-section spring as the main spring offers the advantage that the solids and concentrated slurry are rapidly cleared out as soon as the spring is extended to open the passages 50. The round cross-section of the individual convolutions of the main spring otter thereby a minimum resistance to the outward flow of the solids and concentrated slurries under the eifects of the centrifugal forces. The convolutions of the fiat spring, interspersed between the convolutions of the round cross-section main spring serve as a sealing medium to achieve a tight seal between the neighboring convolutions of the round cross-section main spring 37 and to establish the hereinbefore mentioned weir-like bafiies for increasing the effectiveness of the separating action of the apparatus. The use of the flat springs has the further advantage that the round crosssection main spring is not compressed together all the way in the closed position, thus decreasing spring fatigue to acceptable levels.

The coils or springs may be made from any desired suitable material such as metal or plastic or the like. Preferably the round cross-section main spring is made from suitable metal, like steel, and the flat spring is made from a suitable plastic. The flat spring has been illustrated as having a progressively decreasing inner opening from the inlet end toward the liquid discharge end. This particular design aids in the separation of the solids, particularly with slurries in which the densities of the solids and liquids are close. For other kinds of slurries the progressive decrease of the inner diame- .ters of the individual convolutions of the flat spring 40 may be in the opposite direction, i.e., the smallest diamet'er may be at the end and the largest opening at the liquid discharge end of the helical spring 40.

'In still another embodiment of the apparatus of the invention, the individual convolutions of the fiat spring 40 have a uniform inner diameter which may be just slightly smaller than that of the round cross-section spring, or which may be considerably smaller than the former. Instead of using two interposed springs, one

; may operate the apparatus also with a single main spring. In this case, it is of advantage to provide the main spring with integrated seal members provided on the sides of the individual convolutions of the main spring so as to provide a good seal between the convolutions of the main spring.

As stated hereinbefore, the slurry concentrator of the present invention is not intended to completely separate the liquid and the solids as is the case, for instance, in a centrifuge or in strainer apparatus of the prior art. The concentrator of the present invention is designed to separate, by the use of centrifugal forces, a certain proportion of the liquid, say fifty percent or so, leaving behind a more concentrated slurry than the feed slurry.

Generally, it is preferred in the slurry concentrator of the present invention to continuously feed the incoming slurry to be concentrated at a constant feed rate. However, with certain slurries, and for the achievement of certain effects, it is also possible to modify the feed and adjust the flow rate to the steps of the cycle. The uninterrupted feeding of the slurry, also during the open time of the passages 50, in the cycle of operation has the advantage that the incoming fresh slurry flushes the solids from the inside of the main spring to the outside into the housing 43. The absolute feed rates vary, of course, in accordance with the absolute size of the concentrator and with the particular design of the apparatus, with the nature of the slurry to be concentrated and with the relative desired increase of the concentration of the solids in the slurry. Generally, the feed rates may be greatest in an apparatus of a given size where the differential in the specific weights of the solid phase and of the liquid phase is greatest. Thus, depending on the relative specific weights of the solid and liquid, optimum feed rates in an apparatus of given size may vary in the ratio of one to twenty, or more. Additional increases of flow rates are possible by increasing the centrifugal forces etfectingthe separation, either by increasing the rate of axial rotation of the springs and/or by increasing the diameter of the coil springs.

It is to be understood that the drawings and descriptive matter are in all cases to be interpreted as merely illustrative of the principles of the invention, rather than as limiting the same in any way, since it is contemplated that various changes may be made in the various elements to achieve like results without departing from the spirit of the invention or the scope of the appended claims.

I claim:

1. A slurry concentrator comprising: [axially closable and openable helical spring means, having an inlet end and a discharge end, mounted for substantially axial rotation; means for rotating said spring means; slurry delivery means at the inlet end for feeding slurry to be concentrated into the interior of said helical spring means; liquid outlet means for the discharge of separated liquid at the discharge end of said helical spring means; means radially outward of said spring means for collecting the concentrated slurry when the spring means is opened so as to form passages for the periodical discharge of the concentrated slurry from the interior of the helical spring means; and means for cyclically closing and opening said spring means.

2. A slurry concentrator comprising: a housing mounted for rotation around an essentially horizontal axis of rotation; a helical main spring having a plurality of convolutions; a second helical spring with helical convolutions helically interposed between the convolutions of said main spring, such that a tubular passage is defined; said springs having an essentially horizontal axis of rotation and having an inlet end at one side and a discharge end at the other side; said springs being mounted coaxially and being supported in said housing for axial rotation with the housing; the inlet end of said main spring being fixedly connected to said housing and the discharge end of said main spring being mounted for reciprocatory coaxial movement; slurry inlet means at the inlet end of said tubular passage for feeding the slurry to be concentrated into the interior of said tubular passage; coaxial liquid outlet means for the discharge of separated liquid at the discharge end of said tubular passage; circumferential slurry outlet means in said rotatable housing for the discharge of the concentrated slurry; means elfecting coaxial reciprocation of the discharge end of said helical springs such that the springs are alternatingly compressed into a closed position and extended into an open position so as to form passages for the periodical discharge of the concentrated slurry from the interior of the tubular passage; and driving means for rapid rotation of said housing and of said helical springs around their common axis of rotation.

3. The slurry concentrator of claim 2 wherein the individual convolutions of the main spring have a circular cross-section and the convolutions of the said second spring have a flat cross-section with a variant width radially so as to form weir-like bafiles within said tubular passage.

4. The slurry concentrator of claim 3 in which the width of the weir-like battles formed by the individual convolutions of the flat helical spring increases progressively from one end of said fiat spring to the other.

5. The slurry concentrator of claim 4 in which the width of the weir-like bafiies is least at the inlet end of the tubular passage and greatest at the outlet end thereof.

6. A slurry concentrator comprising: an essentially conical housing having an inlet end at the apex of said cone and an outlet end at the base of said cone; said housing being mounted for rotation around an essentially horizontal axis of rotation; a first helical spring mounted coaxially in said housing for rotation with the housing and fixedly connected at one to the inlet end of said housing; the other end of said first spring being mounted for reciprocatory axial movement; a second helical spring with its coils being alternatingly interposed between the coils of said first spring, the coils of both springs defining together a tubular structure; the individual convolutions of said first spring having a round cross-section and the individual convolutions of said second spring having an essentially rectangular cross-section, with a gradually increasing radial width from the inlet end of said housing toward the outlet end of said housing, such that the radially outer edges of the coils of said first and of said second spring define an essentially cylindrical structure and the radially inner edges of the coilsof the second spring define a conical structure converging from the inlet end of said housing toward the outlet end of said housing; fin-like supporting means mounted longitudinally and coaxially in the housing and defining an essentially cylindrical passage for the sliding support of the cylindrical circumference of the said first and sec-0nd springs; slurry inlet means at the inlet end of said tubular passage for feeding slurry to be concentrated into the interior of said tubular passage; coaxial liquid outlet means for the discharge of separated liquid at the discharge end of said tubular passage; circumferential slurry outlet means in said rotatable housing for the discharge of the concentrated slurry; means for effecting coaxial reciprocation of the discharge end of said helical springs such that the springs are alternatingly compressed into a closed position and extended into an open position; and driving means for effecting rapid rotation of said housing land of said helical springs around their common axis of rotation.

7. A method for concentrating a slurry which comprises: the step of continuously feeding a slurry into a closed helical spring; the step of rapidly rotating the said spring and said slurry so as to separate the slurry into a radially outer portion of slurry which is enriched in solids and a radially inner portion of liquid which is low in or substantially free from solids; the step of discharging the separated liquid generally axially; the step of periodically extending the helical spring so as to form passages between the individual convolutions of the spring for the periodical radial discharge of the portions of the enriched slurry through said passages and the collection of the con- 7 centrated slurry; and the step of compressing the spring so as to substantially close said passages between the individual convolutions of said spring for a new cycle of periodical enrichment and discharge of the enriched slurry.

8. The method of claim 7 in which the time periods for opening and closing of the passages between the individual convolutions of the spring, by extension and compression of the spring, are each a small fraction of the time period for which the spring is rotated in a closed position.

9. The method of claim 7 wherein the spring and slurry are continuously rotated.

10. A method of concentrating a slurry including some and liquid components comprising: feeding a slurry into one end of a circumferentially enclosed space and rotating it while substantially preventing the radial discharge of slurry components so that the slurry is formed into a revolving annulus comprising a radially outer portion enriched in solids and a radially inner portion lower in or free of solid content; removing at least a portion of said radially inner portion generally axially from the space while said space is enclosed; circumferentially opening said enclosed space to permit the radial discharge of said radially outer portion while rotating said annulus; and collecting the radially discharged components.

11. The method defined in claim 10 in which said slurry is fed continuously to one end of said enclosed space and said radially inner portion is removed from the outer end.

References Cited UNITED STATES PATENTS 2,501,179 3/1950 Komline 23320 2,749,031 6/ 1956 Hornbostel 2332() 3,151,628 10/1964 Heckert 137500 ROBERT W. JENKINS, Primary Examiner. 

